This is only used from the wbsearchentities API used for autosuggest. The code currently first gets an exact match on entity id, then exact matches, then in a 3rd query prefix matches if more matches are wanted. Quite many 3 or less letter combinations have enough exact matches. The query in question is a 3rd one. Limiting prefix matches to 4 or more letters is probably sensible for now. Long term I like the cirrus way.